1. Field of the Invention
The present invention relates to an electronic component supplying apparatus which employs a plurality of units for supplying electronic components.
2. Related Art Statement
There is known an electronic component ("EC") supplying apparatus including a plurality of EC supplying cartridges each of which is selectively moved to an EC supplying position for supplying ECs. Each of the cartridges carries a number of ECs, and has an EC supplying portion from which the ECs are supplied. The cartridges are supported on a movable member such that respective EC supplying portions of the cartridges are arranged along a reference line, and cooperates with the movable member to provide a component supplying unit. The unit is moved along the reference line so that an appropriate one or ones of the cartridges is or are moved to the EC supplying position for supplying ECs.
Various sorts of EC supplying cartridges are known. A sort of EC supplying cartridge which is employed in the embodiments described later includes a tape feeding device which feeds an EC carrier tape carrying a number of ECs, for supplying the ECs. Another sort of EC supplying cartridge includes a casing which holds a number of ECs arranged in an array and a vibrating device which vibrates the casing to feed the ECs.
Two or more cartridges of a component supplying unit may carry different sorts of ECs, respectively. Otherwise, two or more cartridges out of three or more cartridges of a unit may carry the same sort of ECs and another cartridge may carry another sort of ECs. In the former case, the unit may supply many sorts of ECs. In the latter case, the unit may supply an increased number of ECs from the two or more cartridges, so that the supplying of ECs from all the cartridges may terminate at substantially the same time. In the latter case, if all the ECs are supplied from one of the two or more cartridges, an operator may replace the said one cartridge with a new one while another or the other of the two or more cartridges supplies the ECs in place of the said one cartridge.
The total number of ECs to be supplied to one object, such as a printed circuit ("PC") board, and/or the total number of sorts of the ECs are/is small in some cases and great in other cases. Since a movable member of a component supplying unit is adapted to the greatest number of ECs and/or the greatest number of sorts, the movable member cannot help having a large size. Accordingly, such a movable-member moving device is needed which can produce a great driving force to move the movable member. In addition, since the large-size movable member has a great inertia, the the movable member cannot be moved at high speeds, which adversely reduces the work efficiency of the EC supplying unit. Moreover, the large-size movable member suffers from the problem that it produces a large vibration when being started and stopped. This problem leads to another problem that an EC picking-up apparatus, such as an EC mounting apparatus, which picks up ECs from each EC supplying cartridge, may fail to pick and hold an EC supplied by the cartridge. Furthermore, in the case where only a single component supplying unit is employed in an EC supplying apparatus, the single unit must be stopped, when all the ECs are supplied from all the cartridges provided thereon, so that the single unit may be replaced by another or new ECs may be fed to the single unit. Thus, the work efficiency of the EC picking-up apparatus is reduced.
The above problems can be solved by employing two component supplying units in an EC supplying apparatus, as disclosed in Japanese Patent Application laid open for inspection under Publication No. 5(1993)-275885. In the case where the total number of ECs to be supplied and/or the total number of sorts of the ECs are/is not so great, all the necessary cartridges may be set on the movable member of one of the units. On the other hand, in the case where the total number of ECs and/or the total number of sorts of the ECs are/is great, all the necessary cartridges may be set separately on the respective movable members of the units. In the former case, only the said one unit is moved for supplying ECs and, in the latter case, the two units are moved individually one by one, or concurrently with each other, for supplying ECs.
The above-indicated document discloses a movable member moving device which moves a movable member of a component supplying unit. The moving device includes a ball screw which is supported by a main frame member of the EC supplying apparatus such that the ball screw is rotatable about an axis line thereof and is not movable in an axial direction thereof. The moving device additionally includes an electric motor which rotates the ball screw, and a nut which is fixed to the movable member and is threadedly engaged with the ball screw. The respective ball screws of the moving devices extend parallel to each other, and are rotated individually one by one, or concurrently with each other, so that the two units are moved individually one by one, or concurrently with each other, for supplying ECs.
However, in some cases, it is not possible to secure a sufficient space in which two ball screws are disposed to extend parallel to each other. In addition, since recently the total number of the ECs, and/or the total number of the sorts of the ECs, to be mounted on a PC board tends toward increasing, there are other cases in which two component supplying units are insufficient and three or more units are necessary. In the latter cases, it is more difficult to secure a sufficient space in which three or more ball screws are disposed to extend parallel to each other. Moreover, in the case where three or more component supplying units are employed, it is almost impossible to employ a movable-member moving device having a conventional construction including ball screws and nuts. Each unit having a nut threadedly engaged with a corresponding ball screw is moved to an EC supplying area in which each unit supplies ECs, and a waiting area which is different from the EC supplying area and in which each unit does not interfere with the EC supplying operation of another unit or the other units. The EC supplying area is common to the three or more units. Accordingly, in the EC supplying area, the three or more ball screws are disposed to extend parallel to one another such that each movable member is moved to the EC supplying area over all the ball screws. To this end, it is required that the width of each movable member, i.e., dimension thereof in a direction perpendicular to the direction of movement thereof be greater than the distance between the two ball screws corresponding to the opposite ends of all the ball screws, respectively. However, each movable member cannot have such a great width and accordingly it is very difficult to employ three or more component supplying units.
By the way, a single ball screw may be used with a plurality of component supplying units in such a way that the ball screw is fixed to a frame member of an EC supplying apparatus, such that the screw is not movable or rotatable relative to the frame member, and a nut threadedly engaged with the screw is attached to each of respective movable members of the units such that the nut is rotatable by an electric motor provided on each movable member. In this case, the single ball screw supports the movable members, irrespective of whether the widths thereof are small or great, such that the movable members are moved one by one or two or more of the movable members are moved concurrently.
In the above case, however, an electricity supplying line connects between an electric-power source which is provided stationarily with respect to the frame member of the EC supplying apparatus, and a motor control device which is provided on each movable member and controls the electric motor thereof, and a signal transmitting line transmits a movable-member control signal to the motor control device. Accordingly, the respective end portions of the electricity supplying line and the signal transmitting line are moved with the movable members but the opposite ends of the two lines are not moved. Therefore, there arise various problems, for example, that the highest speed of each movable member is limited because of an increased mass thereof, that flexible wiring/piping protectors (hereinafter, referred to as the "protectors") which protect the electricity supplying and signal transmitting lines may be damaged, that those lines may break, that noise is produced when the protectors are moved, that the protectors need to have a construction ensuring that they are movable with the movable members, and that the size of the EC supplying apparatus as a whole is increased, or the total number of component supplying units that can be employed is limited, because the protectors occupy a wide space.